Behaviour.register({ 
'#SearchForm_SearchForm_action_results' : { 
onclick : function() { 
         if (document.getElementById('SearchForm_SearchForm_Search').value == "")     
  {       
    alert("Pusty tekst"); 
    return false; 
  }
    
  return true;
} 
} 
});

Behaviour.register({ 
'#Form_LoginForm_action_doLogin' : { 
onclick : 
  function() { 
         if (document.getElementById('Form_LoginForm_Login').value == "" || 
             document.getElementById('Form_LoginForm_Login').value == "login")     
         {       
				    alert("Pusty login"); 
				    return false; 
         }

         if (document.getElementById('Form_LoginForm_Password').value == "")     
         {       
            alert("Puste hasło"); 
            return false; 
         }    
    return true;
  } 
} 
});